A plasma membrane growth inhibiting component has been identified as being one or more membrane proteins, and the work in this laboratory will be concerned with purification of this component. We have preliminary data from another membrane system that isoelectric focusing can be used to separate active membrane proteins while in detergent micelles. We intend to further develop this protocol for separation of our solubulized growth inhibiting component. Assays for activity will be done with reconstituted systems using the procedures developed in the past year. In parallel with isolating the growth inhibiting component, we will start investigating the lipid requirement of the protein. It has been well documented that many integral membrane proteins require a specific lipid environment, and by substituting various combinations of lipids in the reconstituted system, we will be able to determine if the growth inhibiting component has such a requirement. Another possible characterization of this protein is determining whether it is a glycoprotein that requires a carbohydrate moiety for activity. Techniques for separating glycoproteins using affinity chromatography have been developed, and may serve both to identify the protein as a glycoprotein and partially purify if from other protein species. Procedures that hydrolyze carbohydrate groups from proteins will be used to determine functional significance, in the event the growth inhibiting component is identified as a glycoprotein.